underwire

/AH1 N D ER0 W AY0 R/
noun
  1. 1

    A semicircular wire placed in a bra to support the breasts.

  2. 2

    A bra that includes such wires.

verb
  1. 1

    To fix such a wire in place.

Source: https://en.wiktionary.org/wiki/underwire